Recently, Voice Service Indicators have been defined in evolved packet system (EPS) mobile communication systems to coordinate the availability of network services and capabilities of mobile devices. The voice service indicators include, for example:                “IMS Voice over PS session supported” indication;        “Voice Centric” or “Data Centric” indication; and        “CS Voice only” or “IMS PS voice only” or “CS voice preferred, IMS voice secondary” or “IMS voice preferred, CS voice secondary” indication.        
The “IMS Voice over PS session Supported” indication is provided by the network to the user equipment (UE) (given in non access stratum (NAS) registration (e.g. EPS attach) or NAS registration update). The “Voice Centric” or Data Centric” indication and the “CS Voice Only,” “IMS PS voice only,” “CS voice preferred, IMS voice secondary,” or “IMS Voice preferred, CS voice secondary” indication is available on the UE. An operator can configure the “CS Voice Only,” “IMS PS voice only,” “CS voice preferred, IMS voice secondary,” or “IMS Voice preferred, CS voice secondary” indication on the UE.